Manufacturers of microelectronic components use a variety of processing techniques to fabricate semiconductor devices. One technique that has many applications (e.g., deposition, etching, cleaning, and annealing) is known as "plasma-assisted" or "plasma-enhanced" processing. Plasma-enhanced processing is a dry processing technique in which a substantially ionized gas, usually produced by a high-frequency (e.g., 13.56 MHz) electrical discharge, generates active, metastable neutral and ionic species that chemically or physically react to deposit thin material layers on or to etch material layers from semiconductor substrates in a fabrication reactor.
Various applications for plasma-enhanced processing in semiconductor device manufacturing may include high-rate reactive-ion etching (RIE) of thin films of polysilicon, metal, oxides, nitrides, and polyimides; dry development of photoresist layers; plasma-enhanced chemical-vapor deposition (PECVD) of dielectrics, silicon, aluminum, copper, and other materials; planarized inter-level dielectric formation, including procedures such as biased sputtering; and low-temperature epitaxial semiconductor growth processes.
Plasma-enhanced processes may use remotely-generated or locally-generated plasmas. A remote plasma medium is a plasma that a plasma-generating energy source generates external to the process chamber. The plasma is guided into the reactor's process chamber from the remote plasma source and there interacts with the semiconductor wafer for the desired device fabrication processes. A localized plasma is a plasma that a plasma-generating charged electrode forms within the process chamber from a process gas medium capable of generating a plasma. The conventional designs of plasma processing equipment for etch and deposition applications usually employ a 13.56 MHz power source, a 2.5 GHz microwave source or a combination of these energy sources. In conventional systems, a plasma-generating radio-frequency power source connects electrically to an electrically conducting wafer holding device known as a wafer susceptor or chuck. The radio-frequency energy source causes the chuck and wafer to produce a radio-frequency plasma proximate the wafer surface. The plasma interacts with the semiconductor wafer surface.
Opposite and parallel to the wafer and chuck in these systems is a showerhead assembly for injecting the plasma-generating gases into the process chamber. This is known as a parallel-plate configuration due the parallel surfaces of the chuck and showerhead. Typically, the showerhead connects to an electrical ground. In some designs, however, the showerhead assembly may connect to the plasma-generating radio-frequency power source, while the chuck and semiconductor wafer connect to an electrical ground (i.e., so as to have the same potential as the reactor metallic walls). Still other configurations may use a combination of local and remote plasmas. In all of these known configurations, severe limitations exist which limit plasma process flexibility and capabilities.
Limitations associated with using only two parallel plate electrodes include inefficient in-situ chamber cleaning and less than desirable plasma process control flexibility. In particular, the parallel-plate configuration does not provide capabilities for adequate control or adjustment of plasma process uniformity and ion impact energy. Moreover, there is insufficient control over deposited film stress, deposition rate, and deposition uniformity. For example, a change in a plasma process parameter to deposited film stress may adversely affect deposition rate or uniformity, and vice versa. Further, no flexible control over etch rate, etch selectivity, or anisotropy in plasma-enhanced RIE processes exists in these types of systems.
Consequently, there is a need for a plasma fabrication process that overcomes the limitations of known systems to permit efficient in-situ chamber cleaning while providing necessary control capabilities over plasma-enhanced fabrication processes.
There is a need for a method and apparatus for plasma-enhanced device fabrication that offers improved control flexibilities over known methods and apparatuses. In particular, there is a need for a plasma-enhanced device fabrication method and system that improves the control and adjustment of plasma processing uniformity and plasma distribution.
There is a need for a plasma fabrication method and apparatus that offers sufficient and flexible control over film stress, deposition rate, and deposition uniformity.
Furthermore, there is a need for a method and system that permits independent control over plasma etch rate, selectivity, and anisotropy in plasma-enhanced etch processes.